The present invention relates to a pneumatic tire in which the weight-reduction and improvement of durability of a tire are accomplished by employing in a carcass layer cords each comprising non-twisted polyamide monofilaments having a flat cross-section, and more particularly to a pneumatic radial tire suitable for use on automobiles.
Conventionally, pneumatic tires have been proposed in which weight-reduction is accomplished by using non-twisted polyamide monofilament cords having a flat cross-section as reinforcement cords for a carcass layer.
However, the modulus of a polyamide monofilament cord having a flat cross-section is higher than that of a conventional twisted cord, and hence the polyamide monofilament cord has poor flexibility. Due to this, this type of high-modulus polyamide monofilament cords having a flat cross-section have a drawback that when folded up from the inside to the outside of a bead core as cords of a carcass layer, a great magnitude of stress is concentrated at the folded-up end portion which causes the cords to easily separate from rubber, decreasing durability at the bead portion.